The importance of the clinical observer in the development of a white-coat effect in African-American patients with hypertension

Introduction As the office-awake blood pressure (BP) difference (white-coat effect) in African-Americans has not been evaluated, we studied the ethnicity, professional status (nurse versus doctor) and sex of the observer on the white-coat effect in African-American patients with hypertension. Methods Seated clinical BP measurements were obtained in random order by an African-American male research physician, a Caucasian male research physician, and a Caucasian female nurse who is of similar age and clinical experience. Within 1 week, ambulatory BP recordings were performed. Results A total of 65 African-American patients [54 +/- 13 years, 55% women, body mass index (B M 1) 31 +/- 6 kg/m(2), 62% on drug therapy, 28% current smokers] participated in the study. Twenty-two percent had a systolic white-coat effect > 20 mmHg and 49% had a diastolic white-coat effect > 10mmHg (average of all observers). Although there were no differences in the magnitude of the white-coat effect among the three study observers, the primary physician's diastolic white-coat effect was significantly greater than that of the African-American physician (14 +/- 12 vs. 9 +/- 12, P=0.05), but not the systolic white-coat effect (16 +/- 16 vs. 10 +/- 16 mmHg, P=0.09). BMI positively correlated with the systolic and diastolic white-coat effect (r=0.30, P=0.02 and r=0.41, P=0.0001), but this correlation was true only for female patients in multiple regression analyses. BMI significantly predicted the systolic (P=0.043) and diastolic (P=0.004) white-coat effects. Conclusion A white-coat effect is relatively common in African-American patients with hypertension and is the largest when the observer is their usual doctor. The clinical observer's ethnicity or sex does not play an important role in generating a white-coat effect in African-American patients with hypertension.